Studies are in progress on retinal metabolism in frozen sections of retinal layers. The effects of dark-and light-adaptation on high-energy phosphate compounds and cyclic nucleotides are being investigated. ATP, P-creatine, cyclic GMP, cyclic AMP, GTP, and GDP have been measured in 8 retinal layers dark-adapted frogs, and after 2 min or 2 hr of light exposure. In addition the enzyme, guanylate cyclase has been measured under the same conditions.